As is known in the art, hemolysis is the liberation of hemoglobin from red blood cells. Hemolysis may be accomplished by ultrasonic disruption techniques. In ultrasonic disruption, the red blood cells are exposed to an ultrasonic signal which disrupts the cell wall and liberates hemoglobin from the red blood cells.
However if the signal level of the ultrasonic signal is too low, an excessive number of red blood cells remain undisrupted. This results in measurement inaccuracies. On the other hand, if the signal level of the ultrasonic signal is too high, an excessive amount of oxygen may be introduced into the sample or gas bubbles may be introduced into the sample which also results in measurement inaccuracies.
In conventional hemolysis systems, at least a portion of an ultrasonic transducer (i.e. the transducer tip) is disposed in a hemolyzing chamber. An excitation signal is applied to a drive port of the transducer causing the transducer tip to vibrate with an amplitude determined by the load. Conventional ultrasonic transducer driver circuits fail to control the transducer tip motion in response to varying loads in the hemolyzing chamber.
One problem with this approach however, is that as a load disposed in the hemolyzing chamber varies, the transducer provides ultrasonic outputs having varying displacement amplitudes. Thus such driver circuits do not perform adequately in those hemolysis applications where an ultrasonic signal having a relatively constant amplitude is required.
In some applications, for example, the transducer is inherently exposed to varying load conditions. In hemolysis applications wherein the hemolyzing chamber which is initially empty and alternately fills and empties as blood samples of varying characteristics flow therethrough, the load provided to the transducer by the empty and full hemolyzing chamber is substantially different.
It would therefore be desirable in such applications to provide a transducer control system which provides the transducer with a predetermined tip amplitude such that the transducer may provide complete hemolysis of a blood sample while minimizing measurement inaccuracies due to variations in the motion of the transducer tip amplitude.